Large dynamic range silicon photomultipliers for high energy physics experiments

Silicon Photomultipliers (SiPM) are very promising devices for high energy physics (HEP) experiments due to their high photon detection effciency, miniaturized device size and insensitivity to high magnetic fields. Most often detectors are exposed to a high radiation dose for which reason the performance should degrade only minor under the applied radiation load. Decreasing the active depth of a SiPM microcell should help to strengthen the radiation hardness. Additionally for high energy particle physics experiments a large dynamic range is mandatory. This was a further driving reason at KETEK to scale down the microcell pitch and thereby losing only small amount in geometrical efficiency. With these large dynamic range SiPMs a photon detection efficiency in blue spectral range of 32% for 2500 microcells=mm2 and 22% for 4400 microcells=mm2 was achieved. With an improved fabrication technology the dark noise level was decreased to about 250 kHz=mm2 at 20% overvoltage, while the gain variation was still less than 1%=K. Further optimization of the depleted region increased the sensitivity in the output wavelength range of common scintillators (515 nm) by 20% compared to the standard devices. The performance of the KETEK SiPMs will be discussed in detail.